Condition monitoring systems allow for the monitoring of the condition of a system without the need for manual inspection. These systems can be especially important in remote areas or areas which are difficult or dangerous to access, such as the axles and/or bearings of a railway system, particularly one in active operation. In these situations, remote wireless condition monitoring systems can be used.
A remote wireless condition monitoring system may be powered by a battery pack or limited capability power source such as a harvester. A consideration in the design of wireless condition monitoring systems is the time between maintenance which is frequently dictated by the life of their batteries. As a consequence, power management is an important factor in the design of wireless condition monitoring systems because it has immediate impact on maintenance intervals. In these systems, the sensor usually operates from a repetitive cyclic schedule stored in internal memory.
Some wireless condition monitoring systems may rely on external third party systems (such as cellular or wireless networks) to allow them to perform core functions such as data transmission and/or reception. Such external third party systems have the potential to cause the wireless condition monitoring system to behave in an unintended or unpredictable manner. The condition monitoring system may fail to power-on or wake as needed due to events such as loading of a bad firmware image, an incorrect wake schedule which sets an internal real time clock of the condition monitoring system to wake a processor too far in the future or an error encountered during an over-the-air firmware update. The condition monitoring system may fail to power-off or sleep if the processor hangs or an external influence (such as the cellular network or other third party system) causes the condition monitoring system to behave in an unpredictable manner.
Typically, if a device in the field fails to recover due to a firmware or software error, power cycling the sensor or reprogramming the processor with an updated image recovers it from an unknown state. In some cases, a housing containing the system electronics is permanently sealed; there is no ability to power cycle the condition monitoring system or reprogram it using a wired method.
Therefore, solutions preventing the condition monitoring system from behaving in such an unintended or unpredictable manner are desired.